1. Field of the Invention
The present invention relates to a closure assembly for a thermoplastic tube, and particularly for a blood collection tube.
2. Description of the Prior Art
Evacuated and sealed thermoplastic tubes are used for collecting, storing and transporting specimens of blood. The prior art evacuated blood collection tube is used with double ended needle cannula and a tube holder. One end of the needle cannula projects distally from the tube holder, and the opposed end of the needle cannula projects proximally within the tube holder. This prior art assembly is employed by placing the distal end of the needle cannula into communication with a blood vessel of a patient. The prior art evacuated tube then is urged into the tube holder such that the proximal end of the needle cannula pierces the closure of the blood collection tube. Low pressure in the evacuated tube facilitates a flow of blood. After a sufficient volume of blood has been collected, the tube is separated from the holder and shipped to a laboratory for analysis.
Closures of prior art blood collection tubes have taken many forms. All such closures must seal the tube sufficiently for maintaining a vacuum prior to use and for retaining the sample of blood prior to analysis. Prior art closures for blood collection tubes also must be pierceable by a needle cannula, and must be removable or openable to permit access by a probe that extracts blood for analysis.
Some prior art blood collection tubes do not adequately protect health care workers from contact with blood. For example, forces exerted by flowing blood can push the prior art blood collection tube axially out of engagement with the needle cannula. Blood then may flow freely from the needle cannula. In other instances, small droplets of blood may be deposited on an accessible outer surface of the closure as the prior art blood collection tube is separated from the needle cannula. Additionally, some prior art closures are removable from the blood collection tube to enable access by a laboratory probe. The removal of a closure from a tube can create a pressure differential that aspirates or sprays droplets of blood from the tube. The sprayed blood can contact a laboratory technician. Still further, the inner surface of the prior art closure is likely to have direct contact with the blood. Some prior art closures are configured to permit contact with this inner surface after the closure is separated from the tube. Any such contact with a blood sample creates the potential for disease transmission.
Blood samples often are subjected to more than one test. For these situations, it is desirable to reseal the blood collection tube between successive tests. Many prior art closures are not configured for resealing after their initial opening or separation at a laboratory.